In a computed tomography (CT) system, an x-ray source projects a fan-shaped beam that is collimated to lie within an X-Y plane of a Cartesian coordinate system, termed the “imaging plane.” The x-ray beam passes through the object being imaged, such as a medical patient, and impinges upon a multi-row multi-column detector array. The detector array comprises a plurality of detector elements. The intensity of the transmitted radiation is dependent upon the attenuation of the x-ray beam by the object and each detector element of the detector array produces a separate electrical signal that is a measurement of the beam attenuation. The attenuation measurements from all of the detector elements are acquired separately to produce the transmission profile.
The source and detector array in a conventional CT system are rotated on a gantry within the imaging plane around the object so that the angle at which the x-ray beam intersects the object constantly changes. A group of x-ray attenuation measurements from the detector array at a given angle is referred to as a “view” and a “scan” of the object comprises a set of views made at different angular orientations during one revolution of both the x-ray source and the detector. In an axial scan, the projection data is processed to construct an image that corresponds to a two-dimensional slice taken through the object. One method for reconstructing an image from a set of projection data is referred to as the filtered back projection technique. This process converts the attenuation measurements from a scan into integers called “CT numbers” or “Hounsfield units”, that are used to control the brightness of the corresponding pixel on a cathode ray tube display.
A detector array in a CT imaging system comprises a plurality of detector modules. Each detector module has a scintillator array optically coupled to a semiconductor photodiode array. The scintillator array emits light in response to receiving x-rays. The photodiode array detects light output by the scintillator array and generates electrical signals responsive thereto. The scintillator array has a plurality of projecting elements coated with an epoxy. However, when the epoxy is curing on the ceramic scintillator array, the epoxy shrinks after adhesion occurs between the projecting elements and the epoxy. The shrinkage of the epoxy causes a relatively high stress on the interface between the epoxy and the projecting elements that can either crack the elements or deform the elements from a desired shape. Further, because the ceramic projecting elements and the epoxy have different thermal expansion properties, when they both are heated, the epoxy expands a greater amount than the ceramic projecting elements that can crack the elements.
Accordingly, there is a need for a scintillator array that has pixel elements coated with a compound that reduces or minimizes the above-identified problems.